β-Hexosaminidase isoenzyme profiles in serum, plasma, platelets and mononuclear, polymorphonuclear and unfractionated total leukocytes

Objectives: The relative proportion in percentage of the isoenzyme A of β-hexosaminidase (Hex) is the single discriminatory function most frequently used for the biochemical screening of heterozygote Tay–Sachs disease carriers. It has been suggested that the assay of the Hex isoenzymes in homogeneous cell preparations is preferable to that in mixed total leukocytes which present greater interindividual variation. The major aim of our study was the evaluation of this hypothesis. Design and methods: Total Hex and its Hex A and Hex B isoenzymes were determined in different samples of serum and plasma (n = 81) as well as in lysates of platelets (n = 75), and mononuclear (n = 81), polymorphonuclear (n = 81) and mixed total leukocytes (n = 33). Results: The interindividual variations found for % Hex A in the different biological samples were: plasma (CV = 23.4%), platelets (CV = 10.2%), mononuclear (CV = 5.7%), polymorphonuclear (CV = 5.3%) and total leukocytes (CV = 7.1%). Although the relative proportion of Hex A was significantly greater in polymorphonuclear than in mononuclear leukocytes (P < 0.001), a statistical significance was not attained for the correlation between the relative proportions of blood polymorphonuclear cells and Hex A in mixed total leukocytes (r = 0.220). Conclusions: The use of total leukocyte lysates does not appear to introduce a significant increase for the interindividual variation of the Hex A isoenzyme relative proportion in relation to the use of homogeneous cell preparations.